Servo-brake



Nov. 23 1926. 1,608,203 A. DEWANDRE SERVO BRAKE Filed July 1925 3 Sheets-Sheet 1 flfforny Nov. 23 1926.

A. DEWANDRE SERVO BRAKE Filed July 27- 1925 3 Sheets-Sheet 2 Nov. 23 1926.

1,608,203 A. DEWANDRE SERVO BRAKE Filed July 1925 3 Sheets-Sheet 5 F EEFE Patented Nov. 23,1926.-

UNITED STATES, PATENT oFF CE. v

ALBERT niiwnnmm, or 'naussnLs, BELGIUM, nssmnon 'ro 'socmrn 41mm snnvo rnnm DEWANDRE, or LIEGE, BELGIUM.

SERVO-BRAKE.

Application fllcd Ju1y 27, 1825, Serial No.

r of servo brake device which is actuated by means of a so-called fixed control so constructed that it has, among others, the following special characteristics:

When the control lever (the pedal) has been displaced for the purpose of applying or releasing the brakes, this operation 15 accomplished with the intervention of the auxiliary source of energy (for lnstance, the partlal vacuum produced by the suction of the engine) without the-said control lever undergoing either a change of pos1t1on, or

' a change in the effort to which it is sub-' jcc-tedi- The invention, relates to a newform of-v construction of that type of servobrake control device. I

In the present arran ement as, in the 'previous arrangements, t e braking effort is produced by the act-ion of a partialyacuum regulatedby means of a distributing system influenced by he distance which exists between the two parts of a loose connection, which allows a certain amount of play, provided between the control lever and the mechanism.

According to the invention, the distribut: ing system comprises two slide valves connected to each of the said parts of the loose connection respectively. 7

These slide valves,may consist of cylindrical sleeves with a relative axial novement or a relative rotary movem'nt, and they are provided with ports distributed in' three groups: One. grou is in communication with the brake cylin er, a second with the source of paitml vacuum and the third with the-at-J mosphere. I According to the relative position of the said parts of the loose connection, the first group is cut off from the other two or is put, into communication with one or the other of them. The invention relates also to an arrangement generally applicable to'suction actuated brakes and according to which the eontrol lever or pedal exerts at every moment a reaction opposite to the action exerted by the operator in the. direction corresponding toan increasin of the braking intensit this reaction being a function of the bra in intensity. Tn the present construction, the reaction is 46,402, and 1a Belgium om'bei' 7, 1024.

produced by subjecting to the vacuum which acts on. the piston connected 'to" the a brake rodding, a second control lever.- I

By combining this arrangement with. the slide valves above specified, the vslidevalve connected to the control lever may consist of piston connected to the a member subjected to the action ofthe partial vacuum inder.

The invention. also provides for special) forms of construction of the loose connec tion interposed between the control lever and which exists in the brake cylthe brake mechanism, and for the actuation of the distributor by means of the parts of this connection. 1

The accompanying drawings illustrate, by Y 1 I way of example, three forms of construction. In'these drawings j Figure 1 is a diagrammatic view in side elevation, with parts in section,

but the principle ofthe invention. Figure 2 is a perspective view, with parts in secti0n,.show 1ng the means for obtaining the reaction by causing. the artial vacuum to act upon one of the sli e-valves. The position illustrated is that which the parts occupy during the release movement. I Figure 3 ma part-sectional]perspective view of a modlfied construction'compris'ing' slide valves consisting of concentric sleeves having a rotary movement.

The position 1s the same as in Figure 2,

Figure 4 is a perspective view showing a niodification' of the means ofrthe slide valves.

.In Figure 1, the brake mechanism is indicated by at the side of a wheel.

The brakes are applied by transmitting to the cylinder 3 the partial vacuum which for the actuation which brings a shoe carried by a lever 6 situated exists in the suction pipe 1 ofthe engine of the vehicle. The brakes are released by re-- establishing atmospheric pressure in 'the cylinder 3. This operation is controlledyby a distributin system comprising two slide valves61 an 67, 67", 68' and 69. The ports 67" and 67" are in permanent communication with the cylinder" 3, by way'of chamber 65, the port 68 with the atmosphere and the port 69 with 62 provided -with ports such as the suction pipe 1 by way'of chamber 64. The slide valve 61'is connected to thepedal 13, whilethe slide valve 62 is connected to a member 63 which is connected by the link .to the lever 6 so as to enable it to take part in the transmission of the braking force to the brake mechanism, in which transmission the pedal 13 may also take part. This member 63 forms therefore loose connection, that is, a connection allow-- right which cuts off the communication be-' tween the ports 67 and'69. The slide valves have returned into the neutral position. A fresh movement of the pedal 13 in the same direction produces a new braking effort. A movement of the-pedal in the 0 posite-direction is obtained by releasing tie foot pressure thereon, whereupon the pedal is returned, in the manner subsequently explained by the reaction means hereafter described and comprising the piston 60, lever 60 and rOd 60. The return movement of the pedal causesrelease of the brakes due to thefact that the ports67 and 68 are placed in communication with each other and permit air to enter into the brake cylinder 3. The piston4= and the slidevalve 62;

will move towardsthe left, which wiil' brin the relative positions of the slide valves back to the neutral position until a fresh movement is made by the pedal 13. It will thus be seen that a braking efl'ort can be obtained the intensity of which is greater than that which can be obtained by the partial vacuum alone, by moving the .member 63 directly by the pedal 13, .it being understood that the arrangement of the parts is such that the pedal and other movableelements do not occupy their extreme forward positions when the action transmitted to the brakes by the partial vacuum is at its maximum. I 1

A reaction proportional to the'braking intensity is obtained on the pedal by means of the above-mentioned auxiliary piston which is subjected to the vacuum acting on the main piston 4 and is connected to the said pedal sons to transmit to the said pedal the effort to which it is subjected in a direc tion opposite to the direction corresponding to an increasing of the braking intensity,

In Fig. 1, the stem of the auxiliary or reaction piston 60 is loosely connected to the lower portion of the lever or arm 60 which is pivoted at its upper end on a pin 60 and is joined to the pedal 13 by the'rod or link 60" as stated above.

Referring now to Fig. 2, the numerals art of a therein indicate parts similar to those in Fig. 1', the chief difierence being that instead of'the valves being shown as flat slides arranged faceto face, in Fig. 2 they are of cylindrical form and are mounted to have a longitudinal sliding movement within the vacuum cylinder 3. The valve 61, which is formed as a trunk piston and is-o posed to the vacuum piston 4, is connecte by link 61 toone end of a two-armed lever 61", the other end of which is linked by the part 61 to the lower end of the usual brake-operating lever or pedal 13. The second slide valve 62 is formed as an open-ended sleeve which is inter osed between the slide valve 61 and the wa l of the cylinder 3 and which has one end connected by link 62 to one arm of a two-armed lever 62*, the other end of which, by means of a link 62, is operatively connected to a curved lever 66 loosely fulcrume'd on the shaft 13 that forms the fulcrum for the operating pedal 13. The vac= uum piston 4 is linked to one end of a twoarmed lever 4", the other end of which is attached by means of a rod 4" to a slotted or open link 63 which is adapted to transmit its movement to the brake mechanism (not shown) through the intermediary of the connection 5. The parts of the lost-motion .device in this instance are constituted by the operating-pedal 13 and theslotted link 63,

and it is to be ncited that for the purpose a of supporting the free end of the link 63 and b the member 4, the lever 66 is forked so that itcan connect these parts together.

The ,operation is as follows: The illustrated position of the parts shows the slide valves in the position wherein the atmosphere has access to the s ace between the brakepiston 4 and the trun or auxiliary piston whichconstitutes the slide valve 61. The induction pipe 1 is in communication with a surrounding chamber 64, so that when the ports 67 and 69 therein are in register, the negative pressure or suction prevailing in pipel will be transmitted to the space between the pistons.

. \Vhen a braking action is to be initiated, a movement of the brake pedal in aclockwise direction will, by means of link 61, twoarmedlever 61 and link 61*, cause the trunk piston 61 to move to the left. This will have the effect of first closing the ports 67 and 68, so that the interior of the vacuum cylinder will be cut oii from atmosphere. I The continued movement of the trunk piston will then bring into register the suction ports 67 and 69, whereby a suction action i's'exerted in the space between the two pistons which tends to draw them toward each other. The

resulting movement upon the piston 4, 'by

' plied; and the movement of the trunk piston 61 in the opposite direction, by means of link '61, lever 61 and link 61, will exert a reactionary force against the movement. of the operating pedal 13,. so that the operator receives. an indication of the strength of the braking action which is being 1 ap lied. This action of applying thebrake, sould there be no further movement of the brakeoperatiug pedal, will cause the suction efiort from the induction pipe l-to be cut off,- but will not be such as to open the a-tinos' heric pressure ports, which latter'action is e ected by the movement of the curved lever 66 through link 62, double-armed lever 62 and link 62 to act. upon the sleeve 62 which thereupon moves relatively to the trunk piston 61 to interrupt communication between the suction ports 67" and 69, leaving the parts in a neutral osition with all ports closed. Another bra ing action may then be initiated to apply the brakes and again out off the. suction effort. \Vhen the suction )ower of the induction pipe is exhausted, the brakes may be mechanically applied by being moved into contact with one end of the openlink63.

For release, the foot maybe removed altogether from the'pedal 13, whereby the arts will return into the positions illustrate at-- mospheric pressure being then allowed to pass into the interior of the vacuum cylinder to release the brakes.

Referring now to Fig.3: The parts in this modification are generally similar to those. shown in Fig. 2; but instead of the slide valves being arranged as longitudinallysliding cylindrical members, they are inthe form of concentric sleeves rotatable about their own axes after'themanner of a plug valve, and are arranged transversely at one end of the vacuum cy inder 3.

For this purpose, the valve 61 has the form of a hollow plug, and the valve 62. consists of a sleeve concentrically mounted thereon. Longitudinal ports 67" and 69 in the plug 61 and. sleeve 62, respectively, are in communication with a duct which leads to the induction pipe (not shown), while ports. 67" and 68 allow atmospheric ressure to be admitted to the interior of t e plug 61. One end of the cylinder. 3 is closed oil by apartition 3 in which are formed suitable bearingsto support the plug 61 and-sleeve 62, and a port 3 is also formed in such partition for coact-ion with ports 3 and 3 in said plug and sleeve, respectively, to enable either suction or atmospheric pressure to act within said cylinder, the ports 3 and 3 being of sufiicient width to remain constantly in registering relation with each other and with port 3".

For effecting the operation of the lug valve 61, one end thereof is fitted with a ever 74 connected by a link 75 to the lower end of the operating mill or lever 13. The vacuum piston 4 1s ed to one .end ofa lever v4 pedal 13 will which, through the medium of a'connecting member 4", is joined to one end of a twoarmed lever 70 fulcrumed at 76 upon the open link 63, the other end of the doublearmed lever 70- being in contact with the lower end of the operating pedal 13. The arts 63 and 70 are supported inthe forke extremity of the curved lever 66 similarly to the arrangement shown in Fig. 2.

In order that thesleeve 62 may be oper ated, its end remote from the lever 74 is fitted with an operating lever 77 which is connected through rod 71 to a crank 78 attached to theshaft 79 which forms the fulcrum of the lever 4. i a

The operation is as follows With the parts inthe position shown-that is to say, with the atmospheric ports '67 and 68 in communication with each other-atmoswith the interior of the vacuum cylinder through the port 3". The suction acting u on piston 4 will thereupon swing lever 4 a ut its fulcrum 79, and by means of connecting member '4 such movement will be transmitted to act not only upon the brake applying connection. 5 but also to swing or loo ress the lever 7 against the brake-operat- I mg pedal 13 in order to produce the reactionary efiort desired. The resulting movement of applying the brakes will then act by means of the rotary or turning movement imparted to shaft 79 through crank 78, rod 71 and lever 77 to out of! communication between the two suction orts, so that the brakes are held on, ready ibr another braking action by-means of the pedal 13. The final releasing action will eventually cause communication to be set up between the atmospheric ports 68 and 67",. whereby the parts Wlll be restored totheir normal position.

Fig. 4 shows that it is also possible to connect a valve such as 62 to the curved arm 66. In such an arrangement, the valve 62, which is not illustrated, is adapted to be eperated 'by' the rod 72, while rod 73 conneete to the operate the other valve -(likewise 'unillustrated) What I claim is .1. In a servo-brake of the type inwhich the-braking force is produced y the action of a partial vacuum on a piston disposed in the brake cylinder and connected to the brake-rodding, the combination, with a control lever, of a distributing system for regulating -the vacuum action comprising two slide valves, one connected to said lever and the other connected to the rodding to cut oil the action produced by the movement of the first one; said valves being provided with ports arranged in three groups, one coinmunicatin with the brake cylinder, a second with t e source of suction, and the third with atmosphere; and a lost-motion-connection between the rodding and the control lever and to the opposed parts of which the valves are connected for bringin the first grou of ports into re 'stration a ternatively with the second or t ird groups or out of registration with both groups according to.

the distance between the said parts of the lost-motion connection.

'2. A servo-brake, according to claim 1 in which one of the valves forms a second piston located in the brake cylinder tobe subjected .to the partial vacuum therein, and has a positive connection with the control lever.

3. In a servo-brake of the type in which the braking force is produced by the action of a partial vacuum on a piston disposed in the brake cylinder and connected to the brakerodding, the combination, ,With a control lever, of a distributing system for regulating the vacuum action, and a lost-motion connection between the rodding and the control lever and with which the distributing system is associated for influencing said system in accordance with the relative play of the parts of such connection; said distributing system including a second piston located in the brake cylinder to be subjected to the vacuum therein and having a positivevcom nection with the control lever.

4. In a servo-brake of the type in which the braking force is produced by the action of a partial vacuum on a piston disposed in the brake cylinder and con- .nected' to the brake-rodding, the combination, with a control lever, of a distributing system for regulating the vacuum action, and a lost-motion connection between connection; said distributing in a direction opposite that required for ap- 4 plying the brakes. i

5. In a servo-brake of the'type in which the braking force isproduced by the action of a partial vacuum on a piston disposed in the rake cylinder and connected with the brake-rodding, the combination, with a con; trol lever, of a distributing system for reg ulating the vacuum action, a lost-motion connection between the rodding and the control lever and with which the distributing system is associated for influencing said system in accordance with the relative play of the parts of such connection; said connection including an arm mounted co-pivotally with the control lever; and a member. forming part of the rodding and supported by said arm.

6. In a servo-brake of the t e in which the braking force is produced y the action of a partial vacuum ona piston disposed in the brake cylinder and connected with the brake-rodding, the combination, with a control lever, of a distributing system for regulating the vacuum action comprising a pair of slide valves, one of which is connected with said lever, a lostmotion connec-. tion between the rodding and the control lever and with which the distributing system is associatedfor influencin said system in accordance with the relative play of the parts of such connection; said connection including an arm mounted co-pivotally with the control lever and movable relatively to the same; and a connection between said arm and the other valve.

In testimony whereof I aflix m signature.

ALBERT DE ANDRE. 

